<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      list-style: none;
    }

    ul {
      width: 960px;
      height: 200px;
      border: 1px solid;
      margin: 50px auto;
      overflow: hidden;

    }

    ul li {
      width: 160px;
      height: 200px;
      float: left;
      transition: width 2s linear;
    }

    ul:hover li {
      width: 100px;
    }

    ul li:hover {
      width: 400px;
    }
  </style>
</head>

<body>
  <ul>
    <li><img src="./images/ad7.jpeg" alt=""></li>
    <li><img src="./images/ad8.jpg" alt=""></li>
    <li><img src="./images/ad9.jpeg" alt=""></li>
    <li><img src="./images/ad10.jpg" alt=""></li>
    <li><img src="./images/ad11.jpg" alt=""></li>
    <li><img src="./images/ad12.jpg" alt=""></li>
  </ul>
</body>

</html>